So how about this, the SCP is an old mirror from 18th century London but it was not just an ordinary mirror.

There is a creature that comes out of it from time to time sneaking around the owners property like when you feel that your not the only one in a room. But this creature is fast and when your not paying attention it grabs you and pulls you in the mirror imprisoning you in what seems to be a mirror dimension but it's like the victims can see who ever is in front of the mirror but you cant see them, all you see is yourself!

The creature resembles a deformed child and it only comes out the mirror when the mirror has been viewed for 5 seconds.

Seems like there are two separate concepts here that you are trying to fit into one. I would concentrate either on a mirror that pulls you into it randomly or a creature that comes from the mirror when you're not looking. Trying to squeeze both in is a recipe for disaster.